1. Field of the Invention
The present invention relates to an optical scanning apparatus that scans a photoreceptor optically and an image forming apparatus provided with the same.
2. Related Art
In an image forming apparatus such as a copier or printer and the like, a surface of a photoreceptor uniformly electrostatically charged by a charging device is optically scanned by an optical scanning apparatus, such that an electrostatic latent image corresponding to image information is formed on the surface of the photoreceptor. Thereafter, the electrostatic latent image is developed by a developing device using a toner as a developer, and visualized as a toner image. The toner image is transferred onto a sheet of paper by a transfer device, and then heated, pressurized and fixed onto the sheet of paper by a fixing device. Ejection of the sheet of paper onto which the toner image is fixed terminates a series of image forming operations.
An optical scanning apparatus that scans a photoreceptor and forms an electrostatic latent image on a surface of the photoreceptor is composed of: a light source; a deflector that deflects a light beam emitted from a light source; an imaging lens that converts the light beam deflected by the deflector into a constant speed scanning light beam; a reflective mirror that guides the constant speed scanning light beam back onto a photoreceptor; a synchronization detector that detects timing for commencement of scanning of the photoreceptor by the light beam; and a synchronization detection mirror that reflects the light beam to be guided to the synchronization detector, that are housed in a housing.
For downsizing and reinforcing such an optical scanning apparatus while maintaining a length of a light path required of an entire optical system, a configuration is proposed, for example. According to the configuration proposed, the housing is configured to be an H-shape with a plate and frame-like side walls surrounding the plate, and the deflector is disposed in a center of the plate. In addition, a plurality of optical components such as the imaging lens and the reflective mirror are allocated to upper and lower spaces inside the housing partitioned by the plate.
However, in the abovementioned configuration, the synchronization detector and the synchronization detection mirror are disposed in the lower space of the housing divided by the plate. Accordingly, a limitation occurs for a space where the synchronization detector and the synchronization detection mirror are disposed. Depending on the length of the light path of the optical system, there may be a problem that the housing is unable to accommodate the synchronization detector or a problem that the housing increases in size even if it succeeds in accommodating the synchronization detector.
In addition, in the abovementioned configuration, an increase in cost may occur as a result of introducing additional synchronization detection lenses and synchronization detection mirrors. Furthermore, a problem associated with faulty detection of synchronization may occur, which is due to positioning error of the synchronization detection lens and the synchronization detection mirror.